Re: [PATCH 1/4 tip/sched/core] sched: rename preempt_notifier tosched_notifier and always enable it

[Ingo Molnar]

* Paul Mackerras <paulus@xxxxxxxxx> wrote:

> Ingo Molnar writes:
> 
> > The sched notifiers and the various event notifiers we have in the same 
> > codepaths should really be unified into a single callback framework.
> > 
> > We have these _5_ callbacks:
> > 
> > ...
> >         perf_event_task_sched_out(prev, next, cpu);
> > ...
> >         fire_sched_out_notifiers(prev, next);
> > ...
> >         trace_sched_switch(rq, prev, next);
> > ...
> >         perf_event_task_sched_in(current, cpu_of(rq));
> > 	fire_sched_in_notifiers(current);
> > ...
> > 
> > That could be done with just two callbacks - one for sched-out, one for 
> > sched-in.
> > 
> > The best way to do that would be to use two TRACE_EVENT() callbacks, 
> > make them unconditional and register to them. (with wrappers to make 
> > it all convenient to use)
> 
> I'd rather 5 explicit direct function calls than two direct calls and 
> five indirect function calls, actually...

Those five callbacks are typically disabled on a regular Linux system. 
So i'd rather have two sites with some NOPs in them. (no branches, no 
calls)

	Ingo
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